Time delay safety interlock for machines



Sept. 10, 1963 FIG'. .3

b "o L L HOc K IIZb J. R. TILBU RY TIME DELAY SAFETY INTERLOCK FOR MACHINES Filed Sept. 4, 1959 1 H001 if 1 Lu Illa 2 Sheets-Sheet 2 nrronusv James R. Tilbury,

p "This invention .relates gener'ally to protective.equip ,mentifor machinery, and pertainsmore particularly to a i time delay safety interlock which maybe selectively manipulatedinto the particularposition best suiting the operating conditions expected to-be'encounte'red.

In the'present day operation'of punch presses, paper shears, plastic molders and the like, it has become almost mandatory that adequate safeguards be adopted for the Minneapolis,

United StatesPatentO centric is a throw 22 attached to a connecting rod. '24. which proper protection of operating personnel. Both the character and degree of safety needed will vary from machine to machine and from job to job. Accordingly, the invention has for one object the provision of a safety interlock system that can be readily adjusted for conditions at hand. More specifically, it is anaim of the present invention to provide a control that is accessible to only qualified super v-isory personnel and in which the desired goals cannot be readily circumvented by the, operator of the machine.

'In other words the system forming the subject matter of l thisinvention is intended to safeguard the operator and is designed to do so in a highly effective and versatile manner even though the nature of the demands thereon may vary rather widely. I

Another object of the invention is to provide a system of the foregoing character that will be comparatively inexpensive to manufacture and which is not apt to get out i of order readily.

' Yet another object is to provide a safety interlock for machinesthat will be exceptionallyreli-able and which possesses certain inherent fail safe, features. I

A still further object is to provide an interlock system that may be quickly installed on a variety of different type of. machines and which lends itself well to association with existing mechanical safety devices.

Other objects will be in part obviousand in part pointed out more in detail hereinafter. t

The invention accordingly consists in the [features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.

In the drawings: 7 FIGURE 1 is a perspective view of a clutch operated press serving as a general illustration of one type of machine where my interlock system will find utility;

FIGURE 2 is a sectional viewtaken in the direction 1 of line 2--2 of FIGURE 1 in order to show to better advantage a typical tnip clutch mechanism which can also be used with presses equipped with my interlock arrangement, and I FIGURE 3 is a schematic view depicting generally the circuitry utilized in the practicing of the invention, but including portions of the machine exemplified in FIG- URE l so that the viewer'may better orient the electrical features with the mechanical details.

Referring now in detail to FIGURE 1, a conventional press has been denoted in its entirety by the reference numeral 10. Actually the specific details of the press 10 are not important to an understanding of the invention, especially since my time delay safety interlock may be employed with presses of different types and for that matter with other classes of machines where an electric control of the contemplated character may be desirable. However, to illustrate the utility and versatility possessed .by the. electrical controljsubsequently to be described,'it

will be advantageous atthis time to point out that the press structure'includes legs 12 and a generally Cshaped,

journal a crankshaft 20x Encircling the crankshaft ecin turn carries a ram 26. The ram 26, of course, co-

operates with a bolster plate 28 anchored to the bed 30 of the press ltl'the ram traversing a reciprocal path denoted by the double-headed arrow 32. I V p Free to rotate on one end of thecrankshaft 20 is a flywheel 34. I The flywheel 34 is driven by 'an electric motor 36 via a ,belt 38 entrained about the periphery of the flywheel 34 and a pulley 40 on the motor 36;; I,

To effect engagement of the crankshaft 20 with the flywheel 34 a pin clutch mechanism is utilized, parts of which appear in both FIGURES 1 and 2. Accordingly, the flywheel 34, or a strike plate associated therewith, is provided with one or more holes or notches for the reception of one end of a clutch pin or bolt 42 slidably carried in a drive collar 44 atfixed to the crankshaftZtl.

clutch finger 46 from the latch bolt 42, there is a bell crank 50 pivotally carried on a pin 52, the bell crank being articulatively connected to the clutch linger 46 via a link 54; A latch pin 56 is carried by the other arm of the bell crank 50 and is engageable in a notch 58 at the upper end of an actuating bar 60. The role played by the bar 60 will be dealt with in more detail hereinafter when describing the manner in which it is moved downwardly to effect a release of the clutch bolt 42. A coil spring 62 normally pulls the upper end of the bar 6tlfagainst the pin 56 to maintain engagement thereof;

I A cam ring 64, which may be a part ofthe collar 44,

is attached to the crankshaft 20 so as to rotate in unison;

. allows finger 46 to return toits pictured position and thereby cause retraction of the clutch bolt 42 To assure returnof the finger 46 to its depicted position, even if spring 62 should Ibreak, positive return of the finger 46 is assured by reason of a roller 74 mounted at the upper end of an obtuse bell crank 7 6 also pivotally supported on the pin'48. Through the agency of a horizontal link 78 connected to the lower end of the bell crank 76, it will be seen that if the roller 74 is struck by the cam 66, the bell crank 76 is rocked in a direction to force the finger 46 upwardly and thereby cause retraction of the clutch bolt 42. v

The manner in which the actuating bar 60 is pulled downwardly to disengage the clutch finger 46 from the spring biased bolt 42 will now be described. From FIG- URES 1 and 3 it will be perceived that the lower end of the bar 60 is provided with a laterally extending portion thereby imparting an L-shaped configuration to the actuating bar. The bar 60 is constrained for ventical sliding motion by a suitable guide at 82.

Through the agency of an operating cylinder 84 having a piston rod 35 therein, with its projecting end aligned with the laterally extending portion dththe bar 60 can be inder 84 is controlled by a solenoid valve having. a valve portion '66 and a solenoid portion 88. The valve86 ing same. p

i to the relay !124 is rectified so that a DC. potential is may" receive under pressure i rorn a suitable "source I such as a compressor 90. 7

Before describing the circuitry constitutingmy time delay safety interlock, reference will he made to a detach able guard 92 unitoompnising a U shaped tframe 94 and aplunality of vertical rods or fingers 96. One end ot-the lname94 is engageable with a guard switch 98 fixedly rnountedfto a bracket 1 projecting from the visible side of the firame 14,there being a similar 'bracket 100 on the othergor concealed side of said frame.

Also, itis contemplated that afoot switch 102 be asso- 1 -ciated with the press 10. Still further, a pair of hand switches 104, 106 are attached on either side of the press.

Attentionis also directedto acontrol box 108 attached to the right sideof the press structure 10, as can be seen inFIGURE 1. The parts played by these various 113a'or 114a.

switchesa nd: the cOntrol' box will become clearer during succeeding description of the circuitry displayed in FIGURE j p I "Referring nowto FIGURE 3 where my time delay safety interlock is] diagramrned, it will first be explained thattthe control box 108: contains several selector switch levels which arejm'eehanically iganged together for opera. unison. fits-schematically presented a selector switch unit 1'10 has beenillustrated-including three switch levels generally indicated by the reference numerals 110a, 1101) land 1100, each level having five stationary con tacts 111, 1-12; 11-3; 114, and 11 5 and a rotatable switch arm 1-16 for selectively engaging each set oat said contacts. In the drawing these contacts and arms have been dis nguished irom each other laytlie sufiix a, b and c in accordance with the use of these letters forindicating the switch levels 110a, 11% and 11%. The switch arrns 11'6a, 116b-and 116a may be mechanically coupled together 'by a shaft 1118- denotedhy as'uccession of horizonin; dashes. A- manipulating knob 119 permits the shaft 118 to be rotated into a desired; angular position.

Alternating current is supplied to the switch levels 110a, 1 b-and 1100 via power lines L and L and adouble poleswitch-120, this same switch furnishing power to the previously 'rnenti'oned flywheel motor 36-. Thus, when the switch 120 is closed; a potentialis immediately applied to each switch 116:1,11619 and 1160. 'Itwill' he pointed out at this time that a plurality of indicating darnps122a, 1122b, "1220, 12261 and 122a are connected' to the various contacts 111a, 1120, 1113c, 114c and 1 150. of the switch-level 1100. These lamps are contained in'the -control hoxval-ong with the switch unit- Lllll. The lampsoficourse signify the particular position in which theswitch arms 1'16a,1'16b and 1160 have been placed, it being remembered that these switch arms are operated in unison by the shaft'118 through the agency o-fthe knob 119. What happens, at each, switchsetting will become clearer; as the-description progresses. However, it will he manifest that] the lamps 3122 provide a visual'indicati'on of the relative'position or? the switch arms- 116 whenever my system is in operation. 7

At thistime attention is drawn to the tact that the hand switches'104, 106 have an inactuated position in which their respective contacts 104a and 106:: are bridged and an actuated position in which their contacts 104]) and 10% are bridged. In other words the contacts 104a,

106a are normally closed, whereas contacts 104b, 1061) are normally open. I V

In series with the contacts 104a, 106a is a relay 124 equipped, with normally open contacts 12411 which are in turn in series with the solenoid 83 operatively associated to the valve 86. The relay 124 is of the slow release. or slow drop out variety by reason or a capacitor 126 shunt- "Dhrou-gh the medium of a diode 128 the power applied thereacross. The circuit through the diode is com pleted to line L through a limiting resistor 130.

Reference has already been made to the guard switch.

It'will be seen from FIGURE 3 that this switch 98 is pro 'well as toL I a Y Y Having in mindthe'mechanical-construction pictured vided with two sets of'lcontacts' 98a and 98b, Ibothxof which "are closed when the guard 92 is in place on the press 10. From the circuit diagram it will be observed that the contacts Si n are connected to switch arm 116a rectly tothe; relay 124 if switch arm 116a isgon contacts nected to the contact arm.-116l r of. switch level 110b, as

in FIGURES 1- and 2 and the circuit 'arrangement'de contacts 111a, 1-111; and: 11:10, respectively, this switchpositioning will serve as a startingpointiorthe operational 1 description. S'ucli a switch positioning is designed for Foot operation'hecause with the line switch 120-c1osed and-the motor 36' running, electric power is immediately suppliedv to the relay 124; by way or the normally closed contacts 104a andlllfia-of the hand 'switdhes104and-106f It will be appreciated that no hand; actuation of these switches. 104, 106 is intended; when the: [foot switch 102.

is who used.

' Withpower supplied :to'tthe relay, via the contacts 104a: and 106a, as above outline-d; this relay picks up owing to the continued electrical pathfurnished \by' the diode 12,85 2 landresistor 13.0; Such action closes thecontact's 124a,.

for operation when;

the valve 86 toyadmitair to'the cylinder 84, thus causing. piston to move downwardly carrying withit'lthe' actuatingrb ar 60.

Without'going into considerable detail, especially since? i some description has already been given regarding the; clutch mechanism, it will be seen that theolutch finger 46 (FIGURE 2). will be tforceddownwardly to permit the clutchbolt 4210 advance under itsspring bias intoren'gagement with the flywheel 34. This of course causes rota-.

tion of the crankshacfit 20. and the ram? 26'nioves down} wardly to effect the desired fabrication.

Even though the operator may keep thefoot switch I 102 closed, the cam 66 will thereafter strike the roller 74 so as to move the hell crank 76 counter-clockwise :as. viewed in: FIGURE 2 to cause the bell crank 50 to withdraw its pin 56 from the notch 58 on the bar 60; Concornitantly with this happening is the return or": the clutch finger, 416 to its depicted position with the consequence that the clutch bolt 42' is retracted from the flywheel 3 4.

It automatic or continuous reciprocation of the ram 26 is desired, the cam 66 can be removed as with subsequently to'be described automatic-types of operation.

Inasmuch as the lamp 122a is in circuit with the'contact 11 1c oi -the switch level 1100 during the foregoing sequence of events, it will beunderstood that this lamp 122a is the only lamp energized at the moment, 'In this way a tell-tale indication is provided, it being planned that the control box 108 beprovided with a suitable legend indicating that the switch unit 110- housed therewithin has been positioned for fFoot operation.

It will be now'assurned that the switch arms 1 16a, 1165: and 11-60 have been rotated by-theknob 119 intorespective engagement with contacts 112a, 1121) and 112s. Owing to the fact that contact 1 12b is in circuit with contacts 98b of the guard switch 98, it is imperative that the guard 92 be installed so that said contacts 98b will be closed. This typeof operation will be termed Right hand non-automatic operation.

' What occurs with this switch setting is that the relay The other contacts 98b, however, are con;

124 will begene-rgized via the contacts 104a and 1961i jnst as with the above-described Foot operation. The i hand switch 104, that is, the switchjnormally actuated by Y the operators left hand and contact 104b-,'is effectively by-passed or, shunted through contacts 9812, theswitch arm 116b and contactIjllZh The contacts 98bgmust, beclosed by the guanine being in place.- i condition-s .thef'circuitry ,of FIGURE/ "3" so that only =the1 switch reamed. be actuated.) Separationof the contacts 106d immediately interrupts the .circuit to the relay 124, but due to its. slow, dropout; characteristic The ard switch as is not at this time utilized. It is not needed because if either hand is removed from the switches 104 and .106 once -.their actuation has been initiated, therel-ay124 will release-before an opportunity is had for-the =cperator to move his hand sufficiently so as to placeit within the danger zone. I v

Assnming,' =though,that the operator follows through with his intended complete actuation of'the hand switches 1104, 106, then an electrical circuit'is established through the contacts 1041), 106b and 124a to the solenoid 88 I .with the result that =the-va1ve 86 isjop'ened and air is thus derived from the action of the capacitor 126,. the relay contacts 124ml remain, momentarily closed. vContinuedf actnationof thehand switch 106 quickly closes the contact-s "106b wherebycurrent c'an'now flowxthrough these contacts 10 6!); via the aforenoted path, which includes.

guardswitch contactsf98b, the switch arm. 1116b, and

/ contact 11212. The'delay-provided thefcapacitorilzfi is purposely of such short time duration ame operator, p willnothave time toI-shift his hand'from the switch 1% toliajflpoint beneath the ram 261withont"the relay 124 "dropping out. It will vbe appreciatedfthat'the relay contacts, 124 must close in orderto energize the solc- J noid'88fto- ;open the valve 86, all as 'desc'ribedin conjunction with the Foot? operation givenhereinbefore.

Inasmuch as the capacitor126 will soon vdisc ha rgeto a level where the relay 124-will not be held in a picked up I condition,'the relay contacts 124a will quickly open so that the solenoid 88-will not become energized. Thus, only one downward stroke of the ram fieb'will occur.

The occurrence of onlyqoneram'stroke i-sfldoubly assured I if. the cam 66 isemployed. Since the'switch arm 1116c during the Right hand non-automatic'is in engage-T ment with contact 1120, it will be appreciated that lamp 12 2 bpis lighted during this phase. I 1

Assuming-now that the switch arms 116a, 116b and 116s are advanced to the contacts 113a, 113b and 1130 I TLRigthl; hand arutorn-atic 1 13a of-switch-level 11%.] Therefore,-unlike the .Right hand non-automatic operation we nowhave established a conductive path through theswitch arm 116a and.

the coritacts98a where the relay124 will remain energized; Under this Right hand automatic; scheme, it.

is onlynecessary to actuate the right hand switch 166 at anytime; and the solenoid 88 will thereby be energized "through contacts 9811, switch arm; 136b, contact 1131;,

' respectively, ofthe switch unit 110, what will be called 1 operation is made possible; Since;contacts 1l2b'and 113bof. the switch level 1113b "are in effeletcommoned, contacts 98b are-again included injthejf circuit; Additionally,ythough, contacts g98a are infill ld fid', because these contacts are connected to contact contacts "10 61 2 and contacts 124a. Furthermore, continued depression or actuation of theswitch 106 will cause the ram 26 (to reoipr-ocat'e in a repeated or tinnous'fashion if cam 65 has been removed.

con-

During the Right hand automatic operation, the

lamp 1220 will be energized, thereby signifying the type of operation that has been selected.

Next to be dealt 'with is whatwill be termed Two. hand "autornat-ic operation. "In this instance, the switch arms 11611161: and 116c are engaged withthe contacts 114a, 114b and 114C, respectively: The relay 124 willv remain pickediip if guard switch contacts 98a are closed, as in (the Right hand automatic operationflWe now i' 'have a 'situaltion where bothhandswitches I04 and 1% must be actuated before a circuit is completed to the sole- I 1 noid .88. .The only electrical roiite possible is through the contacts .1041) and ltlfib, which of course are bridged p when both switches 104 and 196 are actuated. Other- "wise, the, operation is the same as with the one hand operation, described immediately above. Because the switch arm 116s is at this in engagement with con-' tactlldc lamp 1-22d'is energized.

admitted to the operating cylinder 34.

. However, only one strokeof the ram 26 has a chance to. occur if things are functioning according to'plan, for; actuation of the hand switches 104, 106 breaks the circuit to the relay 124 since the'contacts. 104a, 106a open under these circumstances. Becausethe switch arm 1116c is during period engagedwith the contactllSc, the lamp 1222 will be energized toindicate the type 'of controlled operation that may. take" place.

I To sum up the types or operation possible with my time delaysafety interlock'they are atthis time repeate below in the order they have been presented: l

(1). Foot- I (2) Right hand non-automatic I (3 Right hand automatic (4) Two-hand automatic (5) Two hand non-automatic 1 It will o f course be appreciated that the control box 108 will normally be kept locked,thereby'preventing unauthorized access to the switch unit 110 enclosed there within. In this way' the machine equipped with my system of safety interlocking may be set by responsible and informed supervisory personnel for the type: of operation" that will afford'the maximum degree of protection for the particular Work performing operation t'obe undertaken. e e i As many changes could-be made'in the above construction and many apparently widely different embodiments of the invention could be made Without departing from the scope thereof; it is intended that all-matter contained in 1 1e above description or shown in the accompanying drawingsshall be interpreted'as illustrative and not, in a limiting sense.

It is also to be understood that the language used inthe following claims is intended to cover all of the generic and specific cfeatures of the invention herein described and all, statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

- What is claimed:

*1. A time delay safety interlock system for machines comprising a' slow release relay having normally open conswitch means for selectively by-passing the normally closed contacts of said hand switches to provide two hand automatic operation of said machine. f 2. A timedelay safety interlock system for machines comprising a slow release relay having normally open con- 7 A fifth type, of openation is envisaged which will be referred to as Two hand non-automatic operation.

tacts for conditioning operation of the machine with which the interlock system is associated when said relay has been energized to close said contacts, a pair of hand switches each providedv with normally closed contacts in series circuit with said relay via which energization thereof may be effected and also provided with normally open contacts in series circuit with said relay contacts for providing elecoperation ofsaid machine, switch means for selectively lay-passing the normally open c'ontactsof one of said'hand switches to provide onehand operation of said machine,

and switch means for selectively by passing the normally t closed contacts of said hand switches to provide two hand automatic operation of -said machine; when the switch rneans for by-passi-ng the normally open contacts of said one of saidhand switches is not-utilized and to'provide one hand automatic operation wh'en said switch means for lay-passingthe normally open contacts of said hand switches is utilized.

tric power when closed to said relay contacts to then effect switch inparallel with the normally open contactsof said handswitches, said selector switch means having a 1 second contact position for lay-passing the normally lopen 3'. A- time delayasafety interlock system for machines comprising a slow release relay having normally open 6 contacts for conditioning operationof the machine with i I which the interlock system is-,-associated when said relay has been energized: to close said contacts, a pair of hand switches each providedwith normallyclosed contacts in series circuit with saidrelay via which energization thereof may be effected and alsoprovided with normally open contacts in series circuit with said relay contactsfor providing electric. power when closed to saidrela'y 'contacts to then effect operation of saidmachine, selective switch means for selectively bypassing the normally open contacts of one of said hand switches to provide one hand I operation of said machine, and guard actuated contacts in series with said selective switch means, said guard actuated contacts requiring closing in order to accomplish the lay-passing of the normallytopencontact's of said hand.

switches. 1 i

a 41 A time delay safety interlock system inaccordance with the respective switch meanswhich selectively hy-v pass the normally closed contactsof said hand-switches, said guard contacts requiring closing in Order to accomplish the by-passing of the normally closed contacts of said I hand-switches;

5.-A time delay safety interlock system for machines comprising a relay having normally open contacts for conditioning;operation of themachine with which the interlock system is associa-te d'when said relay has been energized to'close-said contacts, a capacitor shuntingsaid relay to impart a slow drop out characteristic thereto,

with claim 2' including' guard actuated contacts in series 7 means ttor impressing a D.-C. potential acrosssaid relay, a pair of hand'swi-tches vliaving =normally closed contacts, in circuit with said relay and said D.-C. potential means and normally open contacts in circuit with the normally I open contacts of said relay, a guard switch having first I and second sets of normally 'openicontacts both'of which sets are closed when a guard'device'has'been properly positioned on said machine, afoot" switch having normally open'contacts, selector switch means having a first contact positionafor connectingthe: contacts of said foot contacts of one of said hand switches, said sel'e otor' switch means having a third contact position for byepassinggthe;

' normally o'penc'ontacts of said one hand switchandaalso for causing .energization of said relay, saidselecto-rswitch means having a fourth contact position for causing ener-f Y'gizatio'nof said relay, and said selector switch means hav-: a

: ing a fifth position in, which no bY'PfiSSihg occurs and};

in which said relay remains d e-energized, said first and;

second guard contacts being arranged in series with said selectorxrneans I 7 a I .7 6. A time delay safety interlock system in accordance with cl-aimS including a lamp for eachof saidfive posi tions and said selector switch means including respective contact means :for eachof said five positions for energizing eachlamp in accordancewith the p articularjposition of said selector switch means. 1 Y

, References Cited in the file this patent UNilTED. STATES PATENTS 1 

1. A TIME DELAY SAFETY INTERLOCK SYSTEM FOR MACHINES COMPRISING A SLOW RELEASE RELAY HAVING NORMALLY OPEN CONTACTS FOR CONDITIONING OPERATION OF THE MACHINE WITH WHICH THE INTERLOCK SYSTEM IS ASSOCIATED WHEN SAID RELAY HAS BEEN ENERGIZED TO CLOSE SAID CONTACTS, A PAIR OF HAND SWITCHES EACH PROVIDED WITH NORMALLY CLOSE CONTACTS IN SERIES CIRCUIT WITH SAID RELAY VIA WHICH ENERGIZATION THEREOF MAY BE EFFECTED AND ALSO PROVIDED WITH NORMALLY OPEN CONTACTS IN SERIES CIRCUIT WITH SAID RELAY CONTACTS FOR PROVIDING ELECTRIC POWER WHEN CLOSED TO SAID RELAY CONTACTS TO THEN EFFECT OPERATION OF SAID MACHINE, AND INCLUDING SWITCH MEANS FOR SELECTIVELY BY-PASSING THE NORMALLY CLOSED CONTACTS OF SAID HAND SWITCHES TO PROVIDE TWO HAND AUTOMATIC OPERATION OF SAID MACHINE. 